BEIJING — It started this week with a call to action from China’s leader, Xi Jinping. Too many of the country’s children need glasses, he said, and the government was going to do something about it.
It ended on Friday with billions of dollars being wiped from the market value of the world’s largest video game company.
New controls on online games were among Chinese authorities’ recommendations for reducing adolescent nearsightedness on Thursday, sending shares in the country’s leading game publisher, Tencent, tumbling the next day. Shares of Japanese game makers like Capcom, Konami and Bandai Namco also fell on Friday, a sign of the size and importance of the Chinese market.
The sell-off is the latest in a series of government-related stumbles for Tencent, one of the world’s largest technology companies. Chinese state media has blamed video games for causing young people to become addicted, lowering their grades and worse. An incident last year, in which a 17-year-old in the southern city of Guangzhou died after playing a smartphone game for 40 hours straight, received wide attention.
As the biggest game distributor in the world’s biggest game market, Tencent has grown fantastically rich in recent years. It has bought up game developers around the world, including the makers of influential titles such as League of Legends and Clash of Clans. It owns a stake in Epic Games, creator of the international blockbuster Fortnite.
Back at home, Tencent also operates China’s most popular messaging app, WeChat, and processes a big chunk of the smartphone payments that are now used to make transactions of all kinds in the country.
But over the last year, Tencent’s hugely profitable game business has come under fire as Beijing takes a more forceful approach to guiding Chinese culture — a reminder of the state’s growing role in deciding the fortunes of the country’s largest and most innovative private companies.
Last year, the Communist Party’s official mouthpiece, the People’s Daily, called the Tencent-developed battle game Honor of Kings a “poison” on young minds. In response, the company imposed limits on the amount of time young people could spend playing it each day.
More recently, Chinese regulators blocked sales of another Tencent title — Monster Hunter: World — because it was deemed too gory. The company’s stock also took a slide after executives said that a bureaucratic reshuffle had slowed the process for getting licenses to make money on new games such as the mobile version of PlayerUnknown’s Battlegrounds.
Tencent’s shares fell 5 percent in Friday trading in Hong Kong. A company spokesman declined to comment.
In China, bad eyesight has become an increasingly common childhood scourge. The state news agency Xinhua reported this week that Mr. Xi was moved to act after reading a press report on the subject. Nearly half of all Chinese are nearsighted, according to Xinhua.
“The vision health of our country’s young people has always been of great concern to General Secretary Xi Jinping,” the news agency wrote, using one of Mr. Xi’s official titles.
The resulting plan, issued on Thursday by the Ministry of Education, directs China’s media regulator to limit the number of new games approved for distribution, although it does not suggest a specific limit. It also encourages the regulator to explore measures to limit the amount of time minors can spend playing games, and to consider a system for rating games for age appropriateness.
Other recommendations in the notice include improving physical education in schools, limiting the amount of written homework given to elementary school students and improving lighting conditions in classrooms.
The link between screen time and myopia, while popularly held, is a matter of continuing study among scientists. A 2015 report by the World Health Organization cited research indicating that nearsightedness was related to less time spent outdoors and more time doing activities such as reading, studying and focusing on screens.
Follow Raymond Zhong on Twitter: @zhonggg.